Thanks to the captures of naval Enigma materials in the spring of 1941, the British had been able to read three-rotor Enigma on the Heimisch network (Dolphin to the British) with little delay until the end of that year. The principal source of cribs for breaking this traffic was the short-signal book captured from U-110, which the U-boats used for making weather reports. The short-signal weather reports were carelessly rebroadcast by German meteorological stations in a less secure code that the British could read. Working back from the readable text of the meteorological stations, the British were usually able to puzzle out the daily key settings for U-boat Enigma with little delay and minimum usage of bombes.
By January 1942, the Germans had issued to the Atlantic and Mediterranean U-boats new four-rotor Enigma machines and a new short-signal book for use on the new U-boat Enigma net, Triton (Shark to the British). Had the British had a copy of the new short-signal book, very likely they could have broken back into Naval Enigma by means of the rebroadcast meteorological traffic. But absent the new short-signal books, they were stymied. They could not read four-rotor Enigma, an incalculable setback.
There were several possibilities for breaking into four-rotor Enigma in use on the Triton (Shark) net. The fastest way was to capture a copy of the new short-signal book. Doubtless that had been one purpose behind the British commando raid in Norway in late December, but no short-signal books had been found. Another way was to feed such cribs as could be obtained from other sources into the three-rotor bombes. But it took three-rotor bombes twenty-six times longer to find the daily settings of a four-rotor Enigma. Yet another way was to build fast, high-technology, four-rotor bombes. The British pursued the first and third possibilities, even though there was much doubt that a four-rotor bombe could be designed and produced in time to influence the outcome of the war.
The loss of Atlantic U-boat Enigma imposed a tremendous burden on Rodger Winn and his assistants in the Admiralty’s U-boat Tracking Room. Although Winn could draw upon a large store of knowledge accumulated during the six months of 1941 when Bletchley Park was reading the Heimisch (Dolphin) network, a steadily improving land-based British HF/DF network and Werft traffic, POW interrogations, photo reconnaissance in the Baltic, and German propaganda in various media glorifying U-boat skippers, he could no longer provide exact and timely tactical information on Atlantic U-boat movements. After the Germans switched to four-rotor Enigma, Winn’s weekly U-boat summary of February 9 was gloomy: “Since the end of January, no Special Information has been available about any U-boats other than those controlled by Admiral Norway. Inevitably the Atlantic picture is ‘out of focus.’ Little can be said with any confidence in estimating the present and future movements of U-boats.”
The British contempt for Admiral King and America’s alleged inability to cope with or its indifference to the U-boat threat has drawn stinging rebukes and silly statements from British and American historians, but none sillier than that of Francis H. Hinsley, the official historian of British intelligence in World War II. In his otherwise superlative history, he writes, in effect, that so inept were the Americans at ASW that the Allied loss of Atlantic U-boat Enigma at the very time Dönitz launched the all-out U-boat attack on the Americas did not really adversely affect the Allies. “Not even the best intelligence about their [U-boat] activities off the American coast,” Hinsley wrote, “would have facilitated either an effective counterattack on them or the effective evasive routing of shipping so long as the U-boats were at liberty, in the absence of air cover, to operate close inshore and, in the absence of a convoy system, to do so against unprotected shipping.”
To the contrary, had the Allies not lost naval Enigma, the story of the U-boat assault on America might have been quite different. Along with other vital bits of information, naval Enigma doubtless would have revealed that:
• The U-boat attack on the Americas was not a token gesture or feint but rather an all-out effort employing every U-boat Dönitz could lay his hands on and increasing in scale week by week.
• The U-boat campaign in United States waters was to include not only the twenty Type IXs existing on January 1, 1942, the status and movements of which were fairly well known to Allied intelligence, but also a mass of Type VIIs, which, owing to their limited range, had not been foreseen as a threat to American waters.
• Some U-tankers were to be employed to support the campaign in the Americas. They were to provide fuel, food, medical backup, and spare parts for both the Type VII and Type IX attack boats, thus increasing the range, endurance, and productivity of both. Had the Allies learned of this important new dimension in the U-boat war much earlier than was the case, they could have planned countermeasures, such as a carrier strike at a refueling rendezvous, when many U-boats were present and relatively vulnerable. As will be seen, for all too many months the British intelligence agencies refused to credit the rumors of “U-tankers.”
• Owing to the close access to deep (hence safer) water, the U-boats were to concentrate attacks off the Cape Hatteras area and off the southern coast of Florida, where the continental shelf was narrowest and most favorable for submarine operations. Had this been known, the Americans could have marshalled their weak ASW forces at those places sooner than they did, especially at Cape Hatteras.
• U-boats were to operate in United States waters not in groups, or wolf packs, as was then standard practice, but singly, maintaining radio silence. Had these important tactical facts been deduced from decrypted Enigma, American naval officers from King down might have been much more willing to risk convoying in those waters despite the dearth of escorts. A single U-boat could usually sink only one or two ships in a convoy before being pinned down or evaded and, while the radio-silence rule was in force, could not summon other boats.
• The big German surface ships (Tirpitz, etc.) were unable for various reasons to make sorties into the Atlantic in early 1942 to attack Allied convoys. Had this been positively known from Enigma, the Americans could have earlier released their heavy naval counterforces at Iceland, Bermuda, and Argentia, and perhaps even reduced the number of destroyers in troopship convoys. If so, destroyers for use in a convoy network along the Eastern Seaboard could have been made available much sooner.
• German codebreakers at B-dienst had made a substantial penetration into Naval Cypher Number 3, employed by the Allies for most convoy operations. According to intelligence historian Hinsley, for about ten months in 1942 (about February 15 to December 15) B-dienst could read “a large proportion of the signals—sometimes as much as 80 percent.” Decrypts of naval Enigma might well have revealed this grave lapse in Allied naval communications security, which in 1942 gave the Germans a decided advantage in the seesaw battle of codebreaking.
To this time there was still no free exchange of cryptographic technology between the British and the Americans. The British had provided Admiral King with Rodger Winn’s estimates on probable U-boat operations in the Atlantic, derived in part from Enigma and Werft, but they had not fully revealed their secret techniques for breaking Enigma. With the formal entry of America into the war and the nearly simultaneous loss of naval Enigma, and the increasing ship losses in American waters, the British finally began to share their hard-earned cryptographic technology with the Americans.
This technology exchange was lent impetus by President Roosevelt and Winston Churchill. On February 25, Churchill wrote an extraordinary private note to Roosevelt, which was hand-carried to Washington in a diplomatic pouch. Churchill asked Roosevelt to “burn” the letter after reading, but the President did not, and a copy was published in 1989 by Louis Kruh.* In part:
One night when we talked late [during the Arcadia Conference] you spoke of the importance of our cipher people getting into close contact with yours. I shall be very ready to put any expert you care to nominate in touch with my technicians. Ciphers for our two navies have been and are continually a matter for frank discussion between our two Services. But diplomatic and military [Army and Air Forces] are of equal importance and we appear to know nothing officially of your versions of these….
In fact, Churchill went on, “some time ago” British codebreakers had cracked some codes used by the American “diplomatic corps.” Churchill had put a stop to that activity “from the moment when we became Allies”(!), as he put it, but he had been advised that the possibility that “our enemies” had also broken these diplomatic codes could not be dismissed.
At this time the American codebreaking agencies were in a swivet, particularly those of the U.S. Navy, which had failed to detect in advance any hint of the Japanese attack on Pearl Harbor. In the weeks following that disaster, a bureaucratic battle for control of that anomalous and vulnerable group had erupted in the Navy Department. The principal contestants had been the new Director of the Office of Naval Intelligence (ONI), Theodore S. Wilkinson, and the Director of the Office of Naval Communications (ONC), Leigh Noyes, and his deputy, Joseph R. Redman. Distrustful of ONI’s ability to do anything right, Admiral King had sided with Noyes and Redman, and therefore ONC had won control of U.S. Navy codebreakers.
Among the many notable changes Noyes and Redman initiated was the bureaucratic beheading of Laurence Safford, who had commanded the Navy code-breaking unit (OP20G) brilliantly for almost six years. Inasmuch as a free exchange of cryptographic technology with the British was in the works and Safford had made no secret of his distrust of and hostility to the British (for not giving bombe technology in exchange for the Purple machine), Noyes and Redman decided to remove Safford from the mainstream. Denying Safford’s appeal to keep his post, on February 14 Noyes transferred him from command of OP20G to OP20Q, an outfit concerned with the security of American (and Allied) codes and research. As one consequence, Safford did not receive a high wartime decoration and was not selected to flag rank, a scandalous injustice in the view of most of the old hands in OP20G.
This demotion naturally angered and depressed Safford. Doubtless it colored a memo he wrote on March 18 to Noyes and Redman. As Safford put it, the reason for the memo was to stress the need to safeguard the secrets of the breaking of Japanese codes by sharply limiting the dissemination of information derived from this source. However, owing to the pessimistic asides in the memo, it has attained near-legendary status among historians of American codebreaking.
Typically Safford opened his memo with a slap at the British. They had done a good job in World War I of DFing U-boats and decrypting U-boat radio traffic, he wrote, then had stupidly and egotistically bragged about it in print after the war. “Apparently it never occurred to the British that the Germans would profit by these revelations,” Safford wrote accusingly.
Admiral Ernest Joseph King, Commander in Chief of the U.S. Fleet (CominCh) from December 20, 1941, and Chief of Naval Operations (CNO) from March 26, 1942. He held those posts throughout the war and retired on December 15, 1945.
President Franklin Delano Roosevelt, onetime Assistant Secretary of the Navy, demanded and got an awesome “two-ocean navy” in World War II but failed to properly prepare the U.S. Navy for the U-boat threat in the Atlantic.
Admiral Adolphus Andrews, Commander in Chief Eastern Sea Frontier, was an able leader, but in 1942 he lacked the “tools” to combat the U-boat assault on the Americas.
Admiral Royal Eason Ingersoll relieved Admiral King as Commander in Chief Atlantic Fleet in December 1941.
Admiral Percy W. Nelles, Chief of the Royal Canadian Naval Staff from 1934 to 1943.
Reinhard Hardegen, skipper of the Type IXB U-123, who led Drumbeat, the U-boat assault on East Coast shipping in January 1942.
Erich Topp, skipper of U-552, launched Drumbeat in Canadian waters. In the war, he sank thirty-four ships for 185,434 tons, to rank fourth among all skippers.
Peter-Erich Cremer, another Drumbeater, commanded U-333 on two patrols to the U.S. East Coast.
The vast majority of all North Atlantic convoys got through unharmed by U-boats. Here a convoy forms up in an East Coast anchorage.
American blimps provided added convoy escort for a limited distance offshore.
The burning American tanker S.S. Robert C. Tuttle struck a mine off Norfolk, Virginia, planted by the Type VII U-701. The Tuttle was salvaged, but American forces sank U-701.
A convoy arrives safely at its destination.
The Duane, one of six big American Treasury-class Coast Guard cutters that also served as convoy escorts in the North Atlantic, plows into typically heavy seas.
The U.S.S. Toucey, a World War I “four-stack” destroyer, commissioned December 9, 1919. President Roosevelt “lent” the British and Canadian navies fifty such vessels in the fall of 1940 in return for base rights at sites in the Western Hemisphere. These and the other American four-stacks served as troop and cargo convoy escorts.
A corvette, the workhorse cargo convoy escort of the North Atlantic. Shown here, the Royal Canadian Navy’s Kitchener. British and Canadian shipyards produced hundreds of corvettes. Cheaply built, miserably wet and brutally uncomfortable, the corvette nonetheless played a decisive role in the Battle of the Atlantic.
A British-built carrier-based Swordfish torpedo bomber. When fitted with radar and depth charges, these old planes served well in the early years of the war as antisubmarine weapons systems.
The long-range Catalina patrol bomber. American and Canadian factories produced 3,290 Catalinas during the war. The Canadians called this plane the Canso, one of which is shown here. Originally designed to be a flying boat, some later versions were fitted with wheels to become amphibians.
The British-designed and built Sunderland flying boat, employed by RAF Coastal Command in antisubmarine operations. The British produced about seven hundred Sunderlands during the war, some of which were supplied to Commonwealth squadrons.
The American-designed Lockheed Hudson, built in America and Britain. Shown here is the newer, slightly larger U.S. Navy version, the Ventura.
The American-designed and -built B-24 Liberator patrol bomber, a highly effective antisubmarine weapon as well as a strategic heavy bomber.
American aircraft attack and sink the Type XB (minelayer-tanker) U-118.
The big Treasury-class Coast Guard cutter Spencer attacks the Type IXC U-175 with a salvo of depth charges.
After blowing U-175 to the surface, a Spencer boarding party attempts but fails to enter the boat to seize intelligence materials.
Final gasp of U-175. The Spencer closes to rescue German survivors.
A famous photograph symbolizing the defeat of the German U-boat force shows a survivor of U-175 pleading for rescue.
Shocked survivors of U-175 huddle on the deck of the Spencer.
As one consequence of the British disclosures, he went on, in World War II “German ciphers and communications procedure are such that the information obtainable by radio is substantially zero.” With the exception of “weather codes” and certain other “minor systems,” Safford continued, the only German naval messages that had been read had been “the result of captures.”
Therefore, he concluded glumly, “our prospects of ever breaking the German ‘Enigma’ cipher machine are rather poor.”
On their part, the British remained contemptuous of the American intelligence setup in general and codebreaking in particular. There was still no centralized intelligence agency in Washington, no place where all the bits and pieces of information on the enemy came together for analysis and dissemination. Codebreakers in the Army, Navy, Coast Guard, and FBI still toiled in nearly complete isolation, more or less competing with one another, rather than working as a unified team, à la Bletchley Park. The pressures of war—the challenge of breaking naval and other Enigmas for one—demanded closer cooperation between British and American intelligence services. It was coming, but the traditional barriers and safeguards gave way all too slowly. Not until April did the British and Americans take positive steps toward meaningful intelligence exchanges.